1. Field of the Invention
The present invention relates to a method of manufacturing a semiconductor device, and particularly to a method of manufacturing a semiconductor device, which is effective for application to a WCSP (Wafer Level Chip Size Package) in which a packaging process step is executed in a wafer process.
This application is counterpart of Japanese patent applications, Serial Number 284526/2003, filed Jul. 31, 2003, and Serial Number 89168/2004, filed Mar. 25, 2004, the subject matter of which is incorporated herein by reference.
2. Description of the Related Art
A package having a size substantially equivalent to that of a semiconductor chip is generally called “CSP (Chip Size Package)”. CSPs obtained by packaging semiconductor chips formed in a semiconductor wafer while a semiconductor wafer state is being held as it is and bringing it into fractionalization, are called “WCSPs”.
As a resin encapsulating process corresponding to one process for manufacturing a WCSP, there has been known a process using a mold upper die and a mold lower die.
There has been known an encapsulating process which makes use of a resin encapsulating die of a semiconductor wafer, which comprises a fixed mold upper die and a movable mold lower die disposed in a relationship opposite to the fixed mold upper die (see, for example, the following patent document 1).
The resin encapsulating process disclosed in the patent document specifically includes the following process steps.
That is, a film is disposed on the fixed mold upper die. A semiconductor wafer is placed on the movable mold lower die with a bump electrode mounting surface (electrode post mounting surface) being held up. A powdered or granular resin material is provided on the bump electrode mounting surface. After these both dies have been clamped, the dies are heated to melt the resin material.
Next, the film is brought into contact with bump electrode leading ends and the resin lying within each die is pressed through the film to thereby seal the bump electrode mounting surface of the semiconductor wafer with the resin. The dies are finally opened to peel off the semiconductor wafer out of the dies. A configuration has been disclosed wherein in this encapsulating process, the interior of each die is evacuated so as to reach a predetermined vacuum state.
Patent Document 1    Japanese Laid Open Patent Application No. 2000-260796
When the resin encapsulating process using the above dies of the WCSP includes the process of directly placing the pre-melting resin on the semiconductor wafer placed on the mold lower die, the pre-melting hard resin is brought into contact with the surface of the semiconductor wafer. Therefore, three is a fear of damage to the wafer surface or a fear of deformation of each bump electrode formed on the wafer. Since the pre-melting hard resin is in contact with the heated semiconductor wafer before the interior of each die is sufficiently brought into vacuum, a collection of air is easy to occur within the encapsulating resin. As a result, there was a fear that voids were apt to occur in the encapsulating resin. The occurrence of such voids means that the yield of each fabricated semiconductor device is reduced.